ABSTRACT
Infrared (IR) radiation falls between the visible and microwave region of the electromagnetic spectrum and promotes transitions in a molecule between rotational and vibrational levels of the ground state of electronic energy. The units employed to measure the band positions in IR spectroscopy are wave number expressed in reciprocal centimeters, wavelength measured in micrometers, and frequency given in reciprocal seconds. Organic and analytical chemists are mostly interested in the very limited portion of IR radiation, generally referred to as the medium IR region, between 4000 and 650 cm-1. IR spectra may be recorded for gases, liquids, or solids. Gases and liquids may be studied directly without diluting the substances. Pure liquids and solutions of solids, liquids, or gases may be studied by IR. IR spectroscopy is one of the most powerful physical techniques available to the chemist for the purpose of studying the chemical structure and many reactions.
